DE19508739C2 - Screw press for melting and processing thermoplastic materials - Google Patents

Description

The invention relates to a screw press according to the preamble of Claim 1.

Such screw presses are generally known from "Walter Mink, Grundzüge der Extrudertechnik", Rudolf Zechner Verlag GmbH ( 1964 ) and are used, for example, in the processing of thermoplastics. Electrically heated heating tapes are particularly widely used for heating the screw cylinder. The power supply lines can be designed differently. For example, they are braided with glass silk and can be guided in flexible metal hoses.

However, heating tapes with rigid feed lines, as shown, for example, in WO 91/09720 A1, are also known. The short supply lines are formed there as metal pipes, in which the heating conductors are shielded from the metallic sheath in addition to the insulation by a filling of a heat-resistant insulating powder such as MgO or Al ₂ O ₃ . Since the insulating powders are hygroscopic, the ends of the lines are usually sealed with a suitable sealing compound, usually silicone rubber. Since the known sealing masses tend to become brittle in the heat, whereby their sealing effect, in particular against moisture, can be considerably impaired, this type of energy supply has shown to be susceptible to faults due to so-called breakdowns or short-circuits caused by moisture penetration.

The generic DE 19 29 757 U discloses an elek trical radiator for plastic injection machines. Around to ensure that the supply of such radiators even better protected against mechanical damage and penetration of hot plastic mass into the Radiator itself is prevented safely, is pre hit that nozzle of the plastic injection machine from an electric radiator is surrounded by means of a tubular, preferably longitudinally slotted instep clamp is held close. The radiator itself has a metallic inner and outer jacket on who are connected and between which an electrical heating resistor with outside electrical supply line is stored. On the outer jacket A rigid pipe socket is tightly connected overhanging at least one strap, and which one Carries out the electrical supply.

Although in addition the use of such pipe sockets be used to protect electrical supply lines is known and this also leads to a certain success on the contributes to the present area proves to be nonetheless disadvantageous that the problems mentioned are not complete can be solved.

In contrast, the present invention is concerned with the Problem of a protected against breakdowns and short circuits  Energy supply to the electrically heated heater belts of a screw press.

The task is according to the invention in accordance with solved claim 1 specified features. Advantageous Ausge Events of the invention are set out in the dependent claims give.

The solution according to the invention stands out on the one hand by from that, for example, deviating from the genus state of the art for each of the two connections lines a separate heat-resistant tube is provided, which in the heating band pointing radially outwards brought.

It should also be borne in mind that each of the tubes is in one common distribution box opens, which is spaced from the actual screw press is provided. This carries already that the entry opening for insertion the electrical connection cable into the heat-resistant pipes before the high temperatures of the heating device on the Screw press is largely protected.

For this purpose, it is also provided that the distribution box is outside the zone of elevated temperature.

Finally, contributes to the solution of the task at that between the distribution box and the screw barrel or the heat acting on the screw cylinder direction a partition is provided by the electrical  Protective pipes are penetrated. This also ensures repeated heat protection that provides the permanently tight feed in the first place the electrical connection line.

The solution according to the invention also differs from the previously published DE 19 48 807 U in that the cap used there is ultimately not a partition that the electrical connection lines separating pipe from the heating tapes and shields. Above all, it is not recognizable here whether a distribution box is provided, and whether that is the connecting line protective pipe flows into this distribution box. In addition is only one tube is provided, in which several electrical Lines are laid, which according to the invention is just now if should be avoided.

For a contact between the respective connection line and safely prevent the pipe surrounding them Connection line inside the pipe by suitable Centering devices are supported. Is preferred however each tube - if necessary in addition to that then advantageously having corresponding passages tongue - with a highly heat-resistant insulating granulate filled and at the end led in the junction box sealed by a suitable seal.

The heating tapes usually consist of one upper and a lower half-shell, each half-shell has its own entrance and exit. she  can be combined into heating tape groups, where then preferably each group has a connection or distribution box is assigned.  

The heating tapes can be supplied with electrical energy, for example depending on the installed heating capacity - ver in different ways. For example, when it comes to energy supply single-phase alternating current which is half of the connecting leads of one Heating tape group in the junction box above the individual heating tapes associated supply lines with the main power supply, the other Half with return lines, possibly with one for all heating tapes common return line.

The interconnection can preferably also be carried out in such a way that each heating band group has only one common supply and Return line is connected to the main power supply while the Interconnection within the individual heating band groups by corresponding accordingly dimensioned, for example made of metal tape bridge takes place. It has been shown that the entire circuit within a heating tape group with only a few, about three or four, metal bridges of different lengths can be implemented.

With a preferred energy supply especially for higher heating outputs The individual heating tape groups are separated by three-phase alternating current compiled so that the number of heating tapes in a group by three is divisible. The individual heating tapes or also the individual Thirds of the respective heating tape group can then be in two-phase or three-phase connection, in the latter case, for example, in a triangle circuit or in star connection, be interconnected, whereby because which usually have the same nominal power of the heating elements Star connection of the neutral conductor can be omitted.

The tubes (protective tubes) for the heating conductors are essentially preferred Chen in the horizontal direction in the junction box and in the  Partition between the casing of the screw cylinder and the connection box with a flexible silicone seal or diaphragm sleeve seals.

The minimum length of the protective tubes should not be less than 100 to 120 mm, are better approx. 150 to 180 mm, the operating temperatures and, if necessary, also take the dimensions of the screw press into account are.

Parallel to the junction box for the energy supply of the heating tapes and above this is in a preferred embodiment of the invention a protective box is arranged, in which all connecting cables of the Tem temperature sensors that are used to measure and control the Temperature in the sections of the heating tapes Screw cylinders are provided.

The inventive arrangement of the electrical Supply lines for the heating tapes and the measuring lines for the Temperature measurement and control in the various cylinder sections the screw press results in a clear cable routing, the necessary effort for maintenance work on the screws press, for assembly and especially for wiring the heater emente greatly reduced and simplified.

So with a corresponding design according to the invention, the Ab stands and the mutual in the distribution boxes Arrangement of the line connections for the heating elements according to the invention - As already mentioned above - for example between the heating tapes and to and from the supply lines through connecting lugs  or metal bridges of just a few, for example three or four uniform basic forms practically all connections between the heating tapes and heating tape halves.

Based on the execution shown in the attached drawing games the invention is explained.

It shows

Fig. 1 side view of a screw press equipped according to the invention;

Fig. 2 top view of exposed heating tape groups;

Fig. 3 cross section of a screw press according to the invention;

Fig. 4 connection between the connecting lines and the common power supply, detail;

Fig. 5 section through a connecting line according to the invention;

Fig. 6 to Fig. 8 Various circuits of the heating tape groups and the individual tapes;

It should first be pointed out that the drawing figures of the Explanation of the invention serving principle sketches are, in which therefore essentially only those related to the subject Details, e.g. T. simplified, are shown.

Fig. 1 shows an inventively equipped, with a Ummante treatment 2 screw press 1 , the box on one side 3 with the main power supply 5 and the return 7 and - in a modified version - the measuring lines summarizing the manifold 7 and has three connection or distribution boxes 4 , above which a protective box 19 accommodating the temperature monitoring 17 of the individual heating tapes 13 is attached.

FIG. 2 shows a view of a section of the screw cylinder 26 provided with heating tapes 13 . The heating tapes 13 are grouped into groups 14 of three or four heating tapes, each of which a connection or distribution box 4 is assigned. However, it is preferred to combine a number of heating tapes that can be divided by 3, since this results in a uniform network load. From the main power supply 5 , a bundle of distributor lines 6 is guided along the screw press 1 , from which the individual distributor line 6 to one of the heating conductors 9 , 11 in the illustration to the respective connecting line 9 of each heating band 13 guided in a tube 10 , leads, while the other connecting line, in the illustration, the connecting line 11 guided in the tube 12 , for example by means of clamping sleeves 30 ( FIG. 4), is connected to a common return line 8 . For the representation selected for the lines in FIG. 2, reference is made to the note at the beginning of the drawing description.

Fig. 3 shows a cross section through the resting on a stand 24 the screw press 1 with an inner cooling air chamber 21, which is supplied by a fan 20 with cooling air, and a cladding 2 äuße ren. Around the screw cylinder 26 , a heating tape 13 is placed, the outgoing from the connections 29 , guided in the tubes 10 , 12 , not shown here, connecting lines 9 , 11 are essentially in the horizontal direction in the distribution box 4 out. One of the connecting lines, here line 9 , is connected there to the connecting end 15 of one of the distribution lines 6 , the other connecting line 11 is fastened to the common return line 8 via a connecting piece 16 with the aid of a clamping sleeve 30 . Heating portions of the screw cylinder through the Heizbandgruppen 14 or the individual heating strips 13 shown are each provided with an underweight body in protective boxes 19 mounted temperature control 17, temperature sensors 18 in the heater band 13 associated section supply the screw cylinder in the screw cylinder 26, the actual values of the temperature.

The cooling air conveyed by the fan 20 (direction of rotation 22 ) mounted underneath the screw press 1 is introduced into the cooling air chamber 21 from below, if necessary, and serves to cool the screw cylinder 26 in a known manner. Through the cooling air outlet 23 , it can leave the chamber 21 again.

In FIG. 4, the connection of the individual distribution lines 6 to the leads 9 and 11, in slightly enlarged representation is shown, wherein the distributor lines are covered by the common return line 8 6. While the connector 16 is connected to the common return line 8 by a clamping sleeve 30 , the terminal ends 15 of the distribution lines are each their line ends.

FIG. 5 shows a cross section through a part of the length of an on-circuit line 9 (or 10) leading the protective tube 10. The tube is filled with an insulating granulate 25 , in addition or alternatively, some centering pieces 31 are provided which, in the case of their arrangement, are advantageously provided with breakthroughs in addition to the granulate filling with its filling. The right end of the tube in the drawing is sealed with a seal 28 . The connecting line 9 protruding from the seal 28 ends in a connecting piece 27 to which the clamping end 15 is fastened.

FIGS. 6 to 8 show examples of different shapes Interconnection bridge with the aid of a few forms uniformly executed metal. In the three examples shown, the heating tapes 13 consisting of two half-shells 13 A and 13 B are combined into three heating tapes 13 comprising heating tape groups 14 .

The energy is supplied in Fig. 6 current on the single-phase AC leading lines 6, 8 (thick solid lines) in Figs. 7 and 6 respectively by the three-phase AC three-phase 8 and in dot-dash lines modification shown in Fig..

In Fig. 6, the heating tapes 13 of a heating tape group 14 are switched in parallel. From the main lines 6 , 8 lead Ver connections 6 A to the supply line 10 , which is located at the input of the upper half-shell 13 A of the first heating tape 13 . The upper half-shells 13 A of the second and third heating tape 13 of group 14 are also connected to the supply line 6 A via the metal bridge 38 .

The coming from the outputs of the upper half-shells 13 A of the heating tapes 13 lines 12 are connected to the respective inputs 12 of the associated lower half-shells 13 B by means of metal bridges 37 leading downwards, while the outputs 10 of the lower half-shells 13 B are connected by a common metal bridge 38 are connected to each other and via line connection 8 A to line 8 .

Here and in the further described switching examples, the various metal bridges are arranged in parallel to one another and parallel to the control box wall planes that the half-shells 13 A, 13 B of the heating strips 13 connecting bridges 37 run in the rear plane, while the inputs 39 and outputs 40 different heating tapes 13 connecting metal bridges 35 , 36 , 38 are in the front level.

In the case of the supply with single-phase alternating current, the two heating band groups 14 shown in FIG. 6 are each connected via the metal bridges 38 to one another and via the supply lines 6 A, 8 A to the main lines 6 , 8 . The same connection of the heating tapes is also possible with a two-phase power supply from a three-phase network, as will be explained in connection with the line 32 shown in broken lines. In this case, the position numbers 33 and 34 in brackets also apply to the other two lines.

The Fig. 6 comprises a total of two Heizbandgruppen 14 with three heating cables. 13 The heating tapes 13 of both heating tape groups 14 are also connected to each other in this case as described above, but the successive heating tape groups 14 are instead of the main lines 6 , 8 here alternately - to ensure uniform loading of the three phases, if possible in the same number - with the main lines 32 , 33 ; 32 , 34 and 33 , 34 connected.

The switching arrangement shown in FIG. 7 shows two heating tape groups 14 of a system fed by three-phase three-phase current. Each heating band 13 of a heating band group 14 is assigned to one of the three lines 32 , 33 and 34 , which are connected via connections 32A 33A and 34A each to an input of one of the heating bands 13 of one of the heating band groups 14 connected here in a delta connection. Here, too, the interconnection is carried out by metal bridges 35 , 36 and 37 arranged in two levels one behind the other. The individual heating tapes 13 and, in the present delta connection, the individual phases 32 , 33 , 34 connect metal bridges 35 , 36 in the front and the connections 37 between the half-shells 13 A, 13 B of the individual heating tapes 13 in the rear level .

Fig. 8 finally shows a switching arrangement for two heating tape groups 14 a system powered by three-phase three-phase system in a star connection. Here, too, each of the individual heating tapes 13 of a heating tape group 14 is assigned one of the phases 32 , 33 and 34 , for which their inputs are connected to these via leads 32 A, 33 A and 34 A. In this switching arrangement, two forms 37 and 38 of the metal bridges are sufficient for the connection. While the bridges 37 connecting the respective half-shells run in the rear plane, the bridges 38 each reaching over the three heating bands 13 of a heating band group 14 and connecting the respective outputs 40 lie in the front plane.

In the arrangements of FIGS . 7 and 8, each heating band group 14 is individually connected. However, it is also possible, for example, to combine six or nine or even a greater multiple of three heating tapes 13 to form a three subgroups - heating tape group 14 and to combine the individual subgroups of a group 14 in series or in parallel as this is shown in the drawing for each consisting of three heating tapes 13 heating tape groups 14 . In any case, the use of the uniformly designed metal bridges 35-38 described above offers the possibility of establishing the necessary connections rationally, cleanly and reliably. In addition, there is a typical image for each type of connection - using certain groups of metal bridges - which makes assembly or connection errors easily recognizable. This simplifies visual control of the electrical wiring work and is less time-consuming.

REFERENCE SIGN LISTING

1

Screw press

2nd

Sheathing

3rd

Junction box

4

Distribution box, junction box

5

Main power supply

6

Distribution lines

7

Return, mass

8th

Return line, neutral conductor

9

Connecting cable

10th

pipe

11

Connecting cable

12th

pipe

13

Heating tape

13

A upper half shell

13

B lower half-shell

14

Heating tape group

15

Connection end

16

Connector

17th

Temperature monitoring

18th

Temperature sensor

19th

Protective box

20th

fan

21

Cooling air chamber

22

Direction of rotation

23

Cooling air outlet

24th

Stand

25th

Insulating granules

26

Screw cylinder, extruder cylinder

27

Connector

28

sealing

29

Heating tape connection

30th

Clamping sleeve

31

Centering piece

32

Line, three-phase phase

33

Line, three-phase phase

34

Line, three-phase phase

35

Metal bridge, bridge

36

Metal bridge, bridge

37

Metal bridge, bridge

38

Metal bridge, bridge

39

Entrance, heating tape entrance

40

Output, heating tape output

Claims (10)

1. Screw press ( 1 ) for melting and processing a thermoplastic with a screw cylinder ( 26 ) and at least one heating tape ( 13 ) which surrounds the screw cylinder ( 26 ) over part of its axial length, the or the heating tapes over two On connecting lines ( 9 , 11 ) with a power supply ( 5 , 7 ) is connected, characterized by the following features

• - The two connecting lines ( 9 , 11 ) are each placed in a separate heat-resistant tube ( 10 , 12 ),
• - Each of the two tubes ( 10 , 12 ) is attached to the heating band ( 13 ) pointing radially outwards,
• - Each of the tubes ( 10 , 12 ) opens into a common, from the screw cylinder ( 26 ) spaced th distribution box ( 4 ),
• - The distribution box ( 4 ) extends along the screw press ( 1 ) and is attached outside the zone of elevated temperature,
• - Within the distribution box ( 4 ) run Ver distribution lines ( 6 ), which connect the connecting lines ( 9 , 11 ) to the common power supply ( 7 ), and
• - The tubes ( 10 , 12 ) pass through at least one partition wall spaced from the screw cylinder ( 26 ).

2. Screw press according to claim 1, characterized in that the tubes passing through the partition ( 10 , 12 ) are radially sealed in the partition. 3. Screw press according to claim 1 or 2, characterized in that the tubes ( 10 , 12 ) between the heating tape ( 13 ) and the distribution box ( 4 ) through a casing ( 2 ) of the screw cylinder ( 26 ) and run in a partition between Sheathing ( 2 ) and distribution box ( 4 ) are radially sealed. 4. Screw press according to one of claims 1 to 3, characterized in that each tube ( 10 , 12 ) filled with highly heat-resistant insulating granules ( 25 ) and at the end in the distribution box ( 4 ) with an end in its area the connecting lines ( 9 , 11 ) sealingly enveloping seal ( 28 ) is sealed. 5. Screw press according to one of claims 1 to 4, characterized in that each tube ( 10 , 12 ), preferably as a metal tube, has a minimum length of approximately 120 mm. 6. Screw press according to one of claims 1 to 5, characterized in that the minimum length of each tube ( 10 , 12 ) is approximately 150 mm, preferably approximately 180 mm. 7. Screw press according to one of claims 1 to 6, characterized in that the connecting lines ( 9 , 11 ) in the protective tubes ( 10 , 12 ) are centered by support sleeves or disks ( 31 ). 8. Screw press according to one of claims 4 to 7, characterized in that the insulating powder serving as the filling ( 25 ) of the protective tubes ( 10 , 12 ) is MgO and / or Al ₂ O ₃ . 9. Screw press according to one of claims 1 to 8, characterized in that parallel to the distribution box ( 4 ) in which the connecting lines ( 9 , 11 ) of the heating tapes ( 13 ) are connected to the common energy supply ( 5 , 7 ), A protective box ( 19 ) is arranged, in which the temperature sensor ( 18 ) for the measurement of the temperature is led into the sections of the screw cylinder ( 26 ) assigned to the heating bands ( 13 ). 10. Screw press according to one of claims 1 to 9, characterized in that the individual heating tape ( 13 ) consists of an upper ( 13 A) and a lower half-shell ( 13 B) and that both half-shells ( 13 A, 13 B) electrically from each other are separated.